Increase version number in index.js

According to recent 4.2.0 release

Author: MariusRumpf

index.js

@@ -2,7 +2,7 @@
 
 var AWS = require('aws-sdk');
 
-console.log("AWS Lambda SES Forwarder // @arithmetric // Version 4.1.0");
+console.log("AWS Lambda SES Forwarder // @arithmetric // Version 4.2.0");
 
 // Configure the S3 bucket and key prefix for stored raw emails, and the
 // mapping of email addresses to forward from and to.